The present invention relates generally to integrated circuits. More specifically, the invention relates to packaging integrated circuits.
An integrated circuit (IC) package encapsulates an IC chip (die) in a protective casing and may also provide power and signal distribution between the IC chip and an external printed circuit board (PCB). An IC package may use a metal lead frame to provide electrical paths for that distribution.
To facilitate discussion, FIG. 1 is a top view of a lead frame panel 100 and attached dice that may be used in the prior art. The lead frame may comprise leads 108, die attach pads 112, ties 116 for supporting the die attach pads 112, and a skirt 120 for supporting the plurality of leads 108 and ties 116. The lead frame panel 100 may be etched or stamped from a thin sheet of metal. IC chips (dice) 124 may be mounted to the die attach pads 112 by an adhesive epoxy. Wire bonds 128, typically of fine gold wire, may then be added to electrically connect the IC chips 124 to the leads 108. Each IC chip 124 may then be encapsulated with part of the leads 108 and the die attach pad 112 in a protective casing, which may be produced by installing a preformed plastic or ceramic housing around each IC chip or by dispensing and molding a layer of encapsulation material over all IC chips 124. FIG. 2 is a cross-sectional view of part of the lead frame panel 100 and IC chips 124. A tape 136 may be placed across the bottom of the lead frame panel 100 and a mold 132, 133, 134 may be placed around the lead frame panel 100. In this example, the mold is clamped on to the tape 136. In other examples, the mold may be clamped on to both the tape layer 136 and part of the lead frame panel 100. An encapsulation material 140 is provided to fill the mold, encapsulating the IC chips 124, the wire bonds 128, and part of the lead frame panel 100. The tape 136 and the clamping by the mold 132, 133, 134 prevents the encapsulation material 140 from passing through the lead frame panel 100. Once the encapsulation material 140 is hardened, the mold 132, 133, 134 and tape 136 may be removed. The encapsulation material 140 may be cut to singulate the IC chips 124 and leads 108.
The current heavy clamping of the tape or lead frame and tape to prevent leakage may tear the tape, which could cause leakage, or may result in uneven clamping, which may cause increased flashing. The tearing of the tape may also make removal of the tape more difficult.
It would be desirable to provide a method of preventing leakage, tearing of the tape, and flashing.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, a variety of techniques is provided for providing encapsulated dice. Generally, a plurality of dice is connected to a first side of a frame. Tape is attached to a second side of the frame. The dice, frame, and tape are placed completely in a mold cavity. A cover is placed over the mold cavity.
Another embodiment of the invention provides a mold for encapsulating dice attached to a first side of a lead frame with a tape layer covering a second side of the lead frame to form a lead frame assembly. The mold comprises a bottom portion with a cavity large enough to contain the entire lead frame assembly and a cover for covering the mold cavity.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.